This application is based upon and claims priority of Japanese Patent Application No. 11-351589, filed Dec. 10, 1999, the contents being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a device to transfer data between a plurality of devices that utilize high frequency. More specifically, the present invention is related to a phase adjustment device that realizes data transmission by adjusting the clock phase of a reception side device, and to an adjustment mechanism that makes the optimum clock phase adjustment. The present invention may, for example, be utilized in communications between processors in multiprocessor systems.
2. Description of the Related Art
Conventional signal transmission systems are disclosed in, for example, Japanese Unexamined Patent Publication No. H11-136312 and Japanese Unexamined Patent Publication No. H11-112483.
FIG. 2 illustrates the signal transmission system disclosed in Japanese Unexamined Patent Publication No. H11-136312. As shown in FIG. 2, the signal transmission system includes a transmission side device 20 and a reception side device 30 which operate synchronously by the same clock generator 51. The transmission side device 20 includes a transmission side pattern generator 21 that generates a signal having a specified pattern in order for the reception side device 30 to determine whether or not the transmission synchronization is correct. The signal having a specified pattern generated by the pattern generator 21 is supplied to output flip-flops 22, which are provided corresponding to each signal line transmitted on a transmission route 10. Pattern signals transmitted to the transmission route 10 are received by the reception side device 30 and are input into input flip-flops 33 corresponding to each signal line. The clock signal transmitted from the clock generator 51 undergoes phase modification by a sampling phase adjustment circuit 31, and is input to the flip-flops 33 as a clock signal that causes the operation of the input flip-flops 33. A control unit 52 generates a phase adjustment signal 41 to designate an amount of modification for phase modification.
The reception side device 30 includes a pattern generator 35. The pattern generator 35 generates the same pattern signal as the pattern generator 21 of the transmission side device 20. The signal having a specified pattern generated by the pattern generator 35 passes through a delay circuit 38 and is input to a comparator 39. The signals output from the input flip-flops 33 pass through respective flip-flops 34 for synchronization and are input to the comparator 39. The signals pass through the synchronization flip-flops 34 because there is the high possibility that the operational clock of the input flip-flops 33 is not synchronized with the operational clock inside the reception side device 30. The synchronization flip-flops 34 are provided to heighten circuit stability and for the comparator 39 to conduct reliable comparisons.
The control unit 52 attempts to synchronize the data transmission by providing an amount of signal delay based on the transmission route 10, and by designating an amount of phase modification that matches the amount of delay to the sampling phase adjustment circuit 31. Information indicating whether or not the two input signals input to the comparator 39 agree is transmitted from the comparator 39 to the control unit 52. The control unit 52 can use this information to determine whether or not the reception side device 30 as a whole is operating normally in relation to the transmission of data signals.
FIG. 3 illustrates the signal transmission system described in Japanese Unexamined Patent Publication No. H11-112483. As shown in FIG. 3, a transmission side device 60 and a reception side device 70 operate synchronously with the same clock 51. The transmission side device 60 includes a pattern generator 61 that transmits test patterns for synchronization adjustment to the reception side device 70 to adjust the phase discrepancy between a plurality of signals transmitted by a transmission route 10 and the test pattern for phase adjustment, which is conducted to adjust the clock phase of the transmitted signal.
A signal having a specified pattern is generated by the pattern generator 61 and supplied to output flip-flops 22 that are provided corresponding to the plurality of signals transmitted by the transmission route 10. The pattern signals transmitted by the transmission route 10 are received by the reception side device 70, and are input into respective sampling signal phase adjustment circuits 76 for every signal line. The sampling signal phase adjustment circuits 76 change the sampling phase according to an adjustment signal designated by a control unit 72. The signals that are output from the respective sampling signal phase adjustment circuits 76 are respectively input into synchronization adjustment circuits 73.
The control unit 72 controls the synchronization adjustment circuits 73, and the amount of transmission delay for each signal line is controlled and input into a reception determination circuit 75. The reception determination circuit 75 detects the delay time discrepancy between signal lines by using the test pattern for phase adjustment to determine whether or not all of the plurality of input signals are the same. Moreover, the reception determination circuit 75 detects the phase shift delay of the transmission route by determining whether or not the received signal is the same as the test pattern for synchronization adjustment. From the results of the above detection, the control unit 72 designates the amount of adjustment to the signal phase adjustment circuit 76 and the synchronization adjustment circuit 73 in order that the reception side device 70 can receive signals normally.
At present, if a device having a low operational frequency must be utilized, when communicating between devices, there is no problem with the signal delay becoming hidden in the clock gap, even if using simple adjustment circuits such as the conventional adjustment circuits. However, in order to notably improve operational frequency, future information processing devices will have significant problems with the delay of signals and the amount of delay between signals, even when transmitting slight distances like those between neighboring circuit boards. Moreover, it is expected that this problem will become even more pronounced in the future as the operational frequencies of processors improve.
Specifically, structural errors during manufacture, such as variations in materials and valid line lengths, or fluctuation errors caused by changes of environmental conditions, such as the temperature and humidity of the signal lines, are the cause of: (1) transmitted signals fluctuating in conjunction with the passage of time; and (2) signal fluctuations causing fluctuation in the amount of phase modification necessary for the reception side device to receive signals normally. It is not possible to have normal signal reception locally when the phase is on the boundary of the transmission cycle, when a specific phase has great noise, or when a phase cannot fulfill the timing restriction for signal transmission from a circuit that is operating according to one clock signal to a circuit that is operating according to another clock signal.
FIG. 4A illustrates a range of what is conventionally considered to be the transmittable amount of phase modification. More particularly, the horizontal axis in FIG. 4 indicates the amount of phase modification, and, the further to the right along the horizontal axis in FIG. 4, the greater the amount of phase modification. As shown in FIG. 4A, point A is a point at which the amount of phase modification is zero (0), specifically, the point at which no reception signal phase modification is conducted, and point B is a point at which the amount of phase modification becomes one (1) cycle. As shown in FIG. 4A, the range of the dashed lines enclosed by the elliptical framework corresponds to the range of the amount of transmittable phase modification, and the part that is indicated by a straight line is the range of the amount of non-transmittable phase modification.
As indicated in FIG. 4A, it appears that, conventionally, the range of the amount of transmittable phase modification exists only in one place, while the value of the amount of phase modification fluctuates during one clock cycle. For this reason, the phase adjustment for each signal line is set to the center point of the amount of phase modification that can be received normally. The hidden assumption is that the distribution of the transmittable adjustment value is distributed to become a single continuous region.
FIG. 4B illustrates the range of transmittable phase adjustment discovered by the present inventors. As shown in FIG. 4B, as the operational frequency of the circuit improves, there are a plurality of ranges of the amount of transmittable phase modification while the value of the amount of phase modification fluctuates one (1) cycle. The widths of the various serial regions vary. This is because, as the operational frequency of the circuit improves, the range of the amount of adjustment that is conventionally considered to be transmittable is actually locally segmented into a plurality of parts. Depending on the viewpoint, it can be said that the range of the amount of transmittable phase modification may be divided into a plurality of regions. Further, this generates the phenomenon that the transmittable regions that have been divided into a plurality of parts each have their own differing widths.
For this reason, if the phase is adjusted to the center point of the optional range of the amount of transmittable phase modification that was discovered unintentionally, for example, if the phase is adjusted in the state indicated FIG. 4B, there is the possibility of selecting the middle region. If the middle region is selected, if outside disturbances cause the signal to fluctuate even a tiny amount, the reception side device will fluctuate outside the range of the amount of phase modification with the reception signal simply being received normally, and, in this situation, there is the problem that stability will be lost.
The present invention provides a signal phase adjustment circuit that can adjust the difference in delay times between signal lines and set an optimum phase even if the distribution of the amount of phase modification that can be normally received is divided into a plurality of continuous regions.
The present invention solves the problems described above by detecting a region having a width of a specified value or more from among a plurality of regions in a series of amounts of receivable phase modification, and utilizes the detected region to set the amount of phase modification.
In accordance with embodiments of the present invention, a signal phase adjustment circuit comprises a clock phase modification circuit to modify a phase of an input clock signal and to output a phase modified clock signal; an input signal adjustment circuit to receive an input data signal and to transmit the data signal, and which operates based on the phase modified clock signal output from the clock phase modification circuit; a reception determination unit to determine a reception status of the data signal transmitted from the input signal adjustment circuit based on a pre-set fixed pattern signal and the data signal transmitted from the input signal adjustment circuit; and a control unit to control an amount of phase modification of the clock phase modification circuit based on the determination results of the reception determination unit, wherein the control unit determines an amount of phase modification from upper and lower limits of an amount of phase modification of a region, among stable phase regions, having a continuous region width of a specified value or more.
The reception determination unit determines that the reception status of the data signal is normal if the pre-set fixed pattern signal and the data signal transmitted from the input signal adjustment circuit agree, and the control unit selects the amount of phase modification based on the normal status of received pattern signals.
In accordance with embodiments of the present invention, a plurality of data signals are input to the input signal adjustment circuit, and the input signal adjustment circuit further comprises an input delay circuit to delay the respective input data signals by a specified amount, wherein the control unit detects stable phase regions of the respective input data signals having a continuous region width of a specified value or more, and wherein the control unit comprises an amount of delay modification determination device and a device to determine the amount of phase modification, wherein the amount of delay modification determination device determines a phase modification standard value as a maximum value from among minimum amounts of phase modification of continuous regions, wherein the amount of delay modification determination device establishes an amount of delay for each input data signal, such that a minimum amount of phase modification of a region, among the stable phase regions, having a continuous region width of the specified value or more agrees with the phase modification standard value, wherein the device to determine the amount of phase modification determines the optimum amount of sampling phase modification from a lower limit and an upper limit of the amount of phase modification of a location that can receive all signals normally, among the continuous regions wherein all the signals are the same, and having a continuous region width of a specified value or more.
In accordance with embodiments of the present invention, the control unit comprises a phase modification designation unit to designate an amount of phase modification in ascending or descending order from a first value to a second value in relation to the clock phase modification circuit, and to detect a minimum amount of phase modification and a maximum amount of phase modification of the stable phase regions having a continuous region width that can receive signals normally of a specified value or more.
In accordance with embodiments of the present invention, the reception determination unit comprises a selection circuit to select a signal from the plurality of input signals, and to determine that a reception state is normal when the selected signal agrees with a signal having a predetermined fixed pattern, and wherein the control unit detects, for each signal selected by the selection circuit, a region having a continuous region width of a specified value or more, from among the regions having an amount of phase modification that can be received normally.
In accordance with embodiments of the present invention, instead of determining the amount of phase modification from the lower limit and upper limits of the amount of phase modification of a region, among stable phase regions, having a continuous region width of a specified value or more, rather, the amount of phase modification is determined from the lower limit and upper limit amounts of the amount of phase modification of a location that can receive all signals normally, among the continuous regions wherein all the signals are the same, and having a largest continuous region width.
In accordance with embodiments of the present invention, a signal synchronization transmission system comprises a transmission device to output specified pattern signals; a transmission route to transmit the pattern signals; and a reception device to receive signals propagated from the transmission route, wherein the transmission device transmits pre-set specified pattern signals to the transmission route, and the reception device comprises a signal phase adjustment circuit generating a fixed pattern signal which is the same as the pre-set specified pattern signals transmitted by the transmission device.